Fluorescent metabolic substances are known from the field of biotechnology. These substances either accumulate solely in certain areas such as—for example—tumors, inflammations or other specific centers of morbidity, and are therefore only present locally, or they are distributed throughout the body but their fluorescent property is only activated in certain regions in particular, e.g. due to tumor-specific enzyme activities. Because of their fluorescent property these substances can be used as markers or marking substances in order to mark or even record a certain area, e.g. an already pathological area. A region that has been fluorescently marked in this way is identified by illumination of said region with light from a special excitation wavelength of the fluorescent dye and detection of the emitted light in the corresponding emission wavelength of the fluorophore. Potential applications of this examination procedure are all near-surface organs within light penetration range and which develop carcinomas, inflammatory processes or other diseases that are receptive to the application of fluorescent substances. Preferred applications would, for example, be examinations of the prostate gland, bowel, gullet, bronchial tubes or vascular system.